The invention relates to a transmission diversity detecting apparatus and the related method applied to a WCDMA system, and more particularly, to a transmission diversity detecting apparatus capable of generating a quality indicator and the related method thereof.
In WCDMA systems, for registration, an user equipment (UE) must obtain certain system information to camp on a cell. For that purpose, the UE usually provides a cell searcher for getting the system information. Generally, after the UE is powered on, the cell searcher is performed to acquire the timing of the cell and the corresponding scrambling code. However, to read the system information from P-CCPCH, the UE must further detect the antenna diversity of the cell. If the use of antenna diversity is unknown to the UE, the UE might wrongly decode signals from the cell and the decoding performance will degrade significantly.
Please refer to FIG. 1 and FIG. 2. FIG. 1 is the schematic diagram of the synchronization channel (SCH) in the non-TXTD mode. FIG. 2 is the schematic diagram of the SCH in the TXTD mode. As shown in the figures, “a” is a flag showing the transmission diversity of the P-CCPCH channel, “cp” is the primary synchronization code, and “cs” is the secondary synchronization code. It should be noted that the sign of the flag “a” would be different in these two modes. For example, the flag “a” is equal to “−1” when P-CCPCH channel is in non-STTD mode and is equal to “1” when P-CCPCH channel is in STTD mode. It is known that the use of antenna diversity on P-CCPCH channel can be detected from the sign of flag “a”. If the sign of the flag “a” is positive, then it is determined to be in Space-Time Transmission Diversity (STTD) mode; otherwise, it is in non-STTD mode. Please note that the use of the transmit diversity on P-CCPCH is independent of the use of the transmit diversity on SCH.
However, in the related art, to detect the antenna diversity, the UE typically needs to estimate the channel response at two antennas of the cell first. That is, the conventional transmission diversity detecting apparatus must perform the channel estimation procedure before determining the flag “a”. Please refer to FIG. 3. FIG. 3 is a schematic diagram of the primary common pilot channel (CPICH1) transmitted by antenna 1 and the secondary common pilot channel (CPICH2) transmitted by antenna 2. As shown in FIG. 3, the CPICH1 and CPICH2 are utilized to transmit the pilot symbols that includes the channel information, which could be either “A” or “−A”. To detect the signs of the flag “a”, it is necessary to use the pilot symbols respectively in CPICH1 and CPICH2 to estimate the channel responses of antenna 1 and antenna 2 first. Once the channel responses of the two antennas are obtained by utilizing these pilot symbols, the related art can further determine the transmission diversity by evaluating the sign of the flag “a”.
The operations of estimating the channel responses h1(i), h2(i) of the two antennas can be represented by the following equations:
                                          h            i                    ⁡                      (            i            )                          =                              [                                                            D                  cp                                ⁡                                  (                  i                  )                                            +                                                D                  cp                  ′                                ⁡                                  (                  i                  )                                                      ]                    ·                      1            2                    ·                                    A              *                                                                      A                                            2                                                          Equation        ⁢                                  ⁢                  (          1          )                    
                                          h            2                    ⁡                      (            i            )                          =                                            (                              -                1                            )                        i                    ·                      [                                                            D                  cp                                ⁡                                  (                  i                  )                                            +                                                D                  cp                  ′                                ⁡                                  (                  i                  )                                                      ]                    ·                      1            2                    ·                                    A              *                                                                      A                                            2                                                          Equation        ⁢                                  ⁢                  (          2          )                    
In Equation (1) and (2), Dcp(i) denotes the first symbol received in the i-th time slot, and Dcp′(i) denotes the second symbol received in the i-th time slot.
Since we don't know if the SCH channel is in the TSTD mode, and the channel compensation by the channel estimation result is ambiguous, the detection of the use of the transmission diversity is therefore not guaranteed in the prior art.